ENDOTHELIAL ACTIVATION IN MONOSODIUM URATE MONOHYDRATE CRYSTAL-INDUCED INFLAMMATION - IN-VITRO AND IN-VIVO STUDIES ON THE ROLES OF TUMOR-NECROSIS-FACTOR-ALPHA AND INTERLEUKIN-1

Objective. There is relatively little direct evidence for the roles of interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) in a ctivating endothelium in vivo. The aim of this study was to use in vit ro and in vivo models to investigate the contribution of these cytokin es to both E-selectin expression and the recruitment of polymorphonucl ear cells (PMN) in monosodium urate monahydrate (MSU) crystal-induced inflammation. Methods. MSU crystals were incubated with freshly isolat ed mononuclear cells, after which the harvested supernatants were test ed for their ability to induce E-selectin expression during coculture with human umbilical vein endothelial cells, Subsequent experiments we re performed with the addition of neutralizing anticytokine antibodies /antisera. The role of TNF alpha was then studied in an MSU crystal-in duced monarthritis model, in the presence or absence of anti-TNF alpha (5 mg/kg intravenously). (99m)technetium (Tc-99m)-labeled PMN cells a nd (111)indium (In-111)-labeIed anti-E-selectin monoclonal antibody (M Ab) 1.2B6 were intravenously administered 1 hours after intraarticular injection to quantify PRiIN recruitment and E-selectin expression in inflamed joints. Results. MSU crystals were a potent stimulus for IL-1 and TNF alpha production by monocytes in vitro, and these cytokines f ully accounted for MSU crystal-stimulated, monocyte-mediated endotheli al activation. In the MSU crystal-induced monarthritis model, TNF alph a blockade was very effective in suppressing both E-selectin expressio n and PMN emigration into the inflamed joints, as judged by gamma-came ra image analysis and postmortem tissue counting following the intrave nous injection of Tc-99m-PMN and In-111-anti-E-selectin MAb. Conclusio n, IL-1 and TNF alpha appear to be the only factors released by monocy tes following incubation with MSU crystals, which induce E-selectin ex pression in vitro, Anti-TNF alpha is effective in suppressing endothel ial activation and PMN recruitment in vivo E-selectin imaging can be u sed to assess the endothelial response to therapy and may prove useful for clinical studies.